Field of the Invention
This invention relates generally to an improved prosthetic heart valve and to an instrument and method for measuring the velocity of heart leaflets moving in a heart valve, in order to monitor valve condition and performance. More particularly, the instrument measures quantitatively a voltage induced by the motion of the heart leaflet in the heart valve.
For several years, both porcine and nonporcine artificial heart valves have been used for replacement of degenerating heart valves. Monitoring the condition of these prosthetic valves is important. Particularly in the case of porcine artificial heart valves, "early calcification and tearing is a life threatening complication that must be recognized promptly and treated by emergency valve replacement." B. F. Lewis, Early Calcification and Obstruction of a Microporcine Bioprosthesis, Annals of Thoracic Surgery, 30(6): 592-4 (Dec. 1980). Several studies indicate that a very large percentage of the recipients of porcine artificial heart valves are susceptible to heart failure due to the tearing and/or calcification of the valve leaflets. J. L. Bosch, Late Tears in Leaflets of Porcine Bioprosthesis in Adults, Annals of Thoracic Surgery, 37(1):78-93 (Jan. 1984). In addition, both porcine and nonporcine artificial heart valves are subject to malfunctions in operation due to degeneration, thrombosis, endocarditis, bacterial infection, etc.
In general, malfunctions of artificial heart valves occur suddenly and without warning. Therefore, recipients of artificial heart valves are subject to a continual possibility of unexpected valve malfunction and deleterious heart failure. To some extent the possibility of malfunction can be evaluated by periodic testing. At present, the most common method of evaluating artificial heart valve operation is by way of an echocardiogram. This test is very expensive and requires a time delay prior to diagnosis of the echocardiogram test results. In addition, this test can only be performed at established health facilities which have suitable echocardiogram equipment and staff personnel trained and qualified for performing the test and interpreting the test results.
Therefore, it is the object of the present invention to provide an improved method of monitoring the operation of an artificial heart valve, which in particular will enable monitoring of subtle changes in the leaflet structure of the valve in an inexpensive, non-invasive, substantially real-time manner, on a continual or periodic basis.